As mines go deeper in pursuit of increasingly scarce ore, higher ground stress is unavoidable. To combat the safety risks that these high ground stresses bring, an increasing number of mines are adding the step of bolting the face to their development cycle. Face bolting is just what it sounds like – in addition to scaling and installing rock bolts and screen in the back and the walls of a drift, the working face is scaled, screened and bolted to provide better protection to the workers exposed to it.
While the safety benefits of face bolting are clear, they do not come without a cost. Traditionally, the extra time and effort required to bolt the face has been a major deterrent. The process of moving equipment in and out of the heading to bolt the walls and back (bolter), then wash and scale the face (scissor lift or MacLean bolter), and finally to bolt and screen the face (jumbo), meant a lot of equipment was tied up to work on one heading, and the logistical difficulties of having the equipment and manpower available in a timely manner made face bolting a headache. This challenge is one that we at MacLean Engineering decided to tackle.
The MacLean solution
At MacLean Engineering, our face bolting solution follows the MacLean philosophy that has been vital to the success of our bolters and other support equipment: provide a way for miners to do their jobs with first-rate safety and productivity. With this objective in mind and knowing that the most significant issue with face bolting is the movement of equipment in and out of the heading, a key part of our solution is the ability to carry out the entire process with one machine. This means no more time wasted waiting for equipment to become available, and no more tying up equipment that could be productively used elsewhere. Equipped with the face bolting option, the MacLean 975 Scissor Bolter can scale, bolt and screen the walls and back; wash and scale the face; and, bolt and screen the face.
Accomplishing this took some outside-the-box thinking. One of the main challenges in designing the face bolting feature was the space available on the bolting platform. Because face bolting requires the boom to be oriented straight out from the deck, the back end of the boom hangs over the rear of the deck and reduces the available space. The solution to this was to shorten the bolting control console and bolt racks, and implement an adjustable handrail system that allows for full deck space in regular bolting mode, and reduced deck space in face bolting mode to accommodate the forward-facing boom. Redesigned wings that fold down flat onto the deck to allow clearance for the forward-facing boom were also incorporated, and additional, moveable drilling lights were added to allow operators to properly illuminate the face.
Putting it to the test
After trialing the face bolting feature at a number of Canadian mines, we can now say that this is a fully commercialized option for the 975 Scissor Bolter. In the most recent trial, which involved putting split set bolts into 5x5m faces, the bolter was consistently scaling, bolting, and screening faces in less than two hours. At faces that didn't require a lot of scaling, the time to do all this was an hour and a half or less. The efficiency of this method was obvious, with the change from regular bolting mode to face bolting mode taking less than 5 minutes and eliminating the much lengthier process of moving equipment in and out of the heading. Customer feedback indicated that there is a lot of value in being able to do it all with one machine, and the results were tangible – they were gaining extra rounds. The trials confirmed success in applying the productivity and safety of the MacLean bolter to the face.
Looking aheadAt MacLean Engineering we strive to continuously adapt our products to the evolving needs of the underground hard-rock mining industry. The face bolting feature for the 975 bolter is one result of this mission and answers the call for a more efficient way to provide a safer environment for miners working at the face. The goal in designing the face bolting feature was to integrate the additional capability of bolting the face without compromising what the bolter already does so well. Accomplishing this took some creativity, but the result is a MacLean bolter that is even more versatile than its predecessors. With this lower-cost and highly productive method, and as more mines expand deeper or into higher ground-stress environments, we are excited to see our machines bolting more faces in the future.
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